JP2008124719A - Wireless communication equipment, wireless communication method and wireless communication program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for performing flow control while keeping impartiality of communication opportunities for respective nodes in a multi-hop communication network. <P>SOLUTION: Wireless communication equipment judges a communication load of a self-node and instructs an adjacent node transmitting packets to the self-node to reduce the transmission rate when judging the communication load to be overload. An adjacent node which transmits the largest quantity of packets in comparison with the number of transmission source nodes or streams (transmission/reception node pairs) relating to packets of the adjacent node, out of adjacent nodes transmitting packets to the self-node is determined as the adjacent node to be instructed to reduce the transmission rate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for controlling a communication amount in a multi-hop communication network.

  In an ad hoc network, communication (multi-hop communication) is performed with a target destination node via relay of one or a plurality of nodes. In such an ad hoc network, routes tend to be aggregated, and it is likely that the same route is shared by a plurality of communications. A wireless access point or the like is an example of a node to which many nodes try to communicate. Since many nodes communicate with the access point, the closer to the access point, the higher the load for relaying packets of other nodes.

  FIG. 13 is a diagram illustrating a situation in which the nodes 1, 4, 5, and 6 are simultaneously transmitting packets to the destination node D. Since communication from the nodes 1, 4, 5 and 6 is directed to the node D, the closer to the node D, the more communication load is applied. In such a situation, the node 1 not only loses the opportunity to transmit its own packet, but also the packets of the nodes 4, 5, 6 are lost in the middle.

  On the other hand, the technologies described in Patent Documents 1 and 2 have a problem that a node serving as a relay node for other communication in an ad hoc network has a reduced transmission opportunity of a packet generated by itself, and the relay packet By setting the priority of a packet generated by itself higher, the possibility that the relay node becomes disadvantageous is reduced.

  In addition, the technique described in Patent Document 3 describes that a node having a large communication load issues a request to switch a transmission mode to an adjacent node. Here, switching of the transmission mode means, for example, in moving picture distribution, changing the data compression method or changing the frame rate, whereby the transmission data amount can be controlled. Therefore, a node with an increased communication load can avoid congestion by instructing an adjacent node to reduce the transmission amount.

  In addition, in the Ethernet (registered trademark) of the half-duplex communication method, there is a technology called back pressure that intentionally transmits a jamming signal (signal) and stops transmission of other nodes for a certain time when a communication load becomes large. It is known (Non-Patent Document 1).

Further, the technology described in Patent Document 4 allows each node in the ad hoc network to exchange load information, knows the load of the entire network, and allocates many communication resources to a high-load node, thereby enabling communication between the nodes. Opportunities are fair.
JP 2004-31542 A JP 2006-101477 A JP 2006-50371 A JP 2005-303828 A Hiroyuki Osaki and three others, "Performance evaluation of ATM LAN switch with back pressure function, maximum throughput analysis", IEICE Transactions, Vol. J78-BI, pp. 179-188, April 1995

  However, in the case of the prior art as described above, the following problems have occurred.

  In the method of transmitting packets with higher priority of the packet generated by the own node as in the techniques described in Patent Documents 1 and 2, although the possibility that the relay node suffers disadvantages can be reduced, each node in the network The opportunity to send cannot be fair. When a plurality of nodes transmit a packet addressed to the same node, the packet transmitted from the node closest to the destination node is given the highest priority, and another packet does not reach.

  The technique described in Patent Document 3 controls the transmission amount by changing the process at the application level of changing the compression method and frame rate of moving images. In other words, it is necessary to describe in each application how to control the transmission amount, and it is difficult to apply it to general ad hoc networks.

  In addition, the back pressure is used in a wired manner. By sending a jamming signal to the corresponding port, transmission can be suppressed only to necessary nodes. However, wireless influences all surrounding nodes. End up. In addition, there is a problem in that all communication is forcibly stopped (regardless of the destination, urgency, and priority) in the node that is notified of jamming.

  In addition, since the technology described in Patent Document 4 is a method for allocating resources after grasping the load information of the entire network, although it is possible to realize a fair communication opportunity, the load information of the entire network is grasped. There is a problem that it takes too much overhead for processing. Also, if the network size increases or the network topology changes in a mobile environment, it will be difficult to share the constantly changing communication load across the network.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for avoiding congestion while maintaining a fair communication opportunity of each node in a multi-hop communication network. It is in.

  In order to achieve the above object, a wireless communication apparatus according to the present invention is a wireless communication system that includes a plurality of wireless communication apparatuses and performs communication between wireless communication apparatuses by relaying one or more wireless communication apparatuses. A wireless communication apparatus, a transmission rate management means for managing the transmission rate of the own node, a receiving means for receiving a packet from an adjacent node, a load determination means for judging the communication load of the own node, and a communication load of the own node Transmission rate suppression requesting means for requesting the adjacent node transmitting a packet to its own node to suppress the transmission rate when it is determined that the node is overloaded.

  Further, the transmission rate suppression requesting unit is configured to set a transmission rate of a packet transmitted from the adjacent node among a plurality of adjacent nodes transmitting the packet to the own node to a number of transmission source nodes related to the transmitted packet. It is preferable to request suppression of the transmission rate for a specific adjacent node that is the highest adjacent node.

  According to this configuration, when the transmission rate of each wireless communication device in the wireless communication system is suppressed to avoid congestion, the transmission rate transmitted from each wireless communication device is controlled to be equal at each node. The In addition, each wireless communication device transmits a transmission rate suppression request based only on information in the own node, and can transmit a transmission rate suppression request without communicating with other nodes, which requires excessive overhead. Therefore, the transmission rate can be suppressed.

In addition, the transmission rate suppression requesting unit may compare a transmission rate of a packet transmitted from the adjacent node among a plurality of adjacent nodes transmitting the packet to the own node in comparison with the number of streams related to the transmitted packet. It is preferable to request the specific neighboring node that is the highest neighboring node to suppress the transmission rate.

  According to this configuration, when the transmission rate of each wireless communication device in the wireless communication system is suppressed to avoid congestion, the transmission rate per stream transmitted from each wireless communication device is controlled to be fair. Is done. In addition, each wireless communication device transmits a transmission rate suppression request based only on information in the own node, and can transmit a transmission rate suppression request without communicating with other nodes, so that no excessive overhead is required. The transmission rate can be suppressed.

  Further, the transmission rate management means manages a transmission rate by adjusting a resource allocated to communication, and the resource is at least one of the number of channels to be used, the bandwidth, the number of slots, or the back-off time. Preferably it is.

  Further, the transmission rate management means sets a transmission rate for each transfer destination to which a packet is transferred, and the transmission rate suppression request means has a packet whose destination is the own node with respect to a specific adjacent node. It is preferable to request transmission to be suppressed.

  According to such a configuration, each node can suppress only the packet transmission rate to the transfer destination node having an excessive communication load and maintain the transmission rate to other transfer destination nodes, so that efficient communication can be realized. is there.

  Further, the transmission rate management means sets a transmission rate for each destination to which a packet is transmitted, the load determination means determines a communication load for each destination node, and the transmission rate suppression request means includes: For communication to a destination node determined to be overloaded, a specific adjacent node that is the adjacent node having the largest amount of transmission packets compared to the number of streams or the number of transmission source nodes is sent to the destination node. It is preferable to request to suppress the transmission rate.

  According to such a configuration, each node can suppress only the transmission rate of packets to a destination node with an excessive communication load and maintain the transmission rate of packets destined for other nodes, thus realizing efficient communication. It is.

  In addition, a wireless communication method according to the present invention includes a plurality of wireless communication devices, and wireless communication performed by a wireless communication device in a wireless communication system that performs communication between wireless communication devices by relaying one or more wireless communication devices. In the communication method, the wireless communication device manages a transmission rate of the own node, receives a packet from an adjacent node, determines the communication load of the own node, and determines that the communication load of the own node is overloaded. The transmission rate of the packet transmitted from the adjacent node among the plurality of adjacent nodes transmitting the packet to the own node is highest compared to the number of transmission source nodes related to the transmitted packet. It is characterized by requesting the transmission rate to be suppressed for a specific adjacent node that is an adjacent node.

  In addition, a wireless communication method according to the present invention includes a plurality of wireless communication devices, and wireless communication performed by a wireless communication device in a wireless communication system that performs communication between wireless communication devices by relaying one or more wireless communication devices. In the communication method, the wireless communication device manages a transmission rate of the own node, receives a packet from an adjacent node, determines the communication load of the own node, and determines that the communication load of the own node is overloaded. Among the plurality of adjacent nodes transmitting packets to the own node, the transmission rate of packets transmitted from the adjacent node is the highest adjacent node compared to the number of streams related to the transmitted packets. It is characterized in that a certain adjacent node is requested to suppress the transmission rate.

  In addition, a wireless communication program according to the present invention is a wireless communication program in a wireless communication system that includes a plurality of wireless communication devices and performs communication between wireless communication devices by relaying one or more wireless communication devices. When the wireless communication device manages the transmission rate of its own node, receives packets from adjacent nodes, determines the communication load of its own node, and determines that its communication load is overloaded Among the plurality of adjacent nodes transmitting packets to the own node, the adjacent node having the highest transmission rate of the packet transmitted from the adjacent node as compared with the number of transmission source nodes related to the transmitted packet. It is characterized in that a specific adjacent node is requested to suppress the transmission rate.

  In addition, a wireless communication program according to the present invention is a wireless communication program in a wireless communication system that includes a plurality of wireless communication devices and performs communication between wireless communication devices by relaying one or more wireless communication devices. When the wireless communication device manages the transmission rate of its own node, receives packets from adjacent nodes, determines the communication load of its own node, and determines that its communication load is overloaded In addition, among a plurality of adjacent nodes that are transmitting packets to the own node, the specified adjacent node that is the highest adjacent node compared to the number of streams related to the packet in which the transmission rate of the packet transmitted from the adjacent node is transmitted It is characterized in that the node is requested to suppress the transmission rate.

  According to the present invention, it is possible to avoid congestion while maintaining a fair communication opportunity of each node in a multi-hop communication network.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings.

(First embodiment)
In this embodiment, an ad hoc wireless communication network is composed of a plurality of movable wireless communication devices. In an ad hoc wireless network, communication between nodes that cannot communicate directly is realized through relaying by other nodes. As described above, the ad hoc wireless network uses multi-hop communication in which communication is performed between a transmission source node and a destination node by a plurality of hops.

  FIG. 1 is a diagram illustrating an example of a network topology of an ad hoc wireless communication system according to the present embodiment. In FIG. 1, nodes connected by solid lines can directly communicate with each other. Specifically, node 1 in FIG. 1 can communicate directly with node D and node 2. A node that can directly communicate with node 1 in this way is called an adjacent node of node 1.

  In FIG. 1, it is assumed that the node D is an access point that provides a connection to the Internet or the like. In such a case, since many nodes in the network try to communicate with the node D, the closer to the node D, the more the communication load increases and congestion occurs. In this embodiment, when the transmission rate of each node (the amount of packets transmitted per unit time) is controlled to avoid congestion, the transmission rate is controlled so that the transmission opportunities of each node are fair. Objective.

<Functional configuration>
A wireless communication apparatus according to this embodiment will be described. First, the wireless communication device in the present embodiment is a movable wireless communication device. Specifically, in addition to things that can carry the device itself, such as notebook computers, mobile phones, PDAs (Personal Digital Assistants), etc., objects that are fixed but installed in automobiles (automobiles) Etc.) is a mobile body, and a wireless communication device that moves is also included. The wireless communication device is configured to include a CPU (Central Processing Unit), a main storage device (RAM), an auxiliary storage device (ROM), a communication interface, and the like connected via a bus as a hardware configuration. .

  FIG. 2 is a diagram illustrating a functional configuration of the wireless communication apparatus according to the present embodiment. In the wireless communication device according to the present embodiment, various programs (OS, applications, etc.) stored in the auxiliary storage device are loaded into the main storage device and executed by the CPU, whereby the packet reception unit 11, the packet determination unit 12, It functions as a packet buffer 13, a load determination unit 14, a communication resource allocation unit 15, a resource allocation packet generation unit 16, a packet transmission unit 17, and a path storage unit 18. In addition, all or part of the functional units of the wireless communication device in the present embodiment may be configured by a dedicated chip.

  Hereinafter, each functional unit of the wireless communication apparatus will be described with reference to FIG. The detailed operation of each functional unit will be described in a processing flow described later, and an outline of each functional unit will be described here.

  The packet receiver 11 receives a transmitted packet. The received packet is sent to the packet determination unit 12.

  When the received packet is addressed to the own node, the packet determination unit 12 passes the packet to the upper layer. If the received packet is addressed to another node and should be relayed, it is stored in the packet buffer 13. If the received packet is a resource allocation packet (resource allocation packet), the packet is sent to the communication resource allocation unit 15.

  The packet buffer 13 temporarily stores a packet to be transmitted. Specifically, a packet transmitted from an upper layer (application program) and a packet relayed by the own node are stored.

  The load determination unit 14 determines whether the communication resources currently allocated to the own node are excessive or insufficient by looking at the change in the amount of packets accumulated in the packet buffer 13.

  The communication resource allocation unit 15 adjusts communication resources allocated to the own node according to a communication resource allocation packet (described later) transmitted from the adjacent node. Further, the communication resource allocation unit 15 increases the amount of communication resources allocated to the packet transmission unit 17 when the communication resource allocated to the node by the load determination unit 14 is insufficient (communication load is overloaded). . Here, when the communication resource of the own node cannot be increased any more, a notification to reduce the transmission amount is given to the upper layer of the own node or to the adjacent node that sends the packet to be relayed Request reduction of communication resources. Since the number of packets transmitted per unit time is reduced by reducing communication resources, a communication resource reduction request corresponds to a transmission rate suppression request.

  On the other hand, if the communication load is small compared to the communication resources allocated to the own node, it is allowed to increase the allocation of communication resources to the upper layer or an adjacent node that sends a packet to be relayed Make a notification.

Note that the communication resource is a resource (resource) related to communication, and the amount of packets (transmission rate) that can be transmitted per unit time improves as the number of communication resources is increased. As an example of communication resources, the number of channels, the bandwidth, the number of slots, the back-off time, and the like can be increased according to the wireless communication scheme used by the wireless communication apparatus. Here, with regard to the number of channels, the bandwidth, and the number of slots, the larger the number of allocations, the more resources (the transmission rate becomes larger), while the backoff time is increased as the allocated backoff time is shorter.

  When the communication resource allocation unit 15 determines that the communication resource allocation unit 15 requests the adjacent node to reduce the communication resource or allows the communication resource allocation to be increased, the resource allocation packet generation unit 16 A packet (resource allocation packet) to be transmitted is generated.

  The packet transmission unit 17 transmits the packet stored in the packet buffer 13 and the resource allocation packet generated by the resource allocation packet generation unit 16. At this time, the packet generation unit 17 transmits the packet within the range of communication resources allocated to the own node by the communication resource allocation unit 15.

  The route storage unit 18 stores route information and stores which adjacent node should be next transmitted for each destination node. The route information may be created by any existing technology, for example, it can be created by an AODV (Ad-hoc On-demand Distance Vector) protocol or OLSR (Optimized Link State Routing) protocol. The route information may be created by other methods. In addition to creating a route information table in advance using a proactive routing protocol, route information is acquired at the time of packet transmission using a reactive routing protocol such as DSR (Dynamic Source Routing) protocol. It does not matter as a configuration.

<Processing flow>
Next, a processing flow of flow control of the wireless communication device in the present embodiment will be described using the flowchart of FIG. The flowchart of FIG. 3 is a process performed at regular intervals.

  First, the load determination unit 14 checks the packet buffer 13 (S101), and compares the current communication load with the communication resources allocated to the own node (S102). This comparison is performed by determining whether the amount of packets accumulated in the packet buffer 13 is increasing, decreasing, or unchanged.

  When the communication load is larger than the communication resource, that is, when the number of packets in the packet buffer 13 is increased, the process proceeds to step S103.

  In step S103, it is determined whether it is possible to allocate communication resources to the own node (S103). That is, the communication resource currently allocated to the own node is compared with the communication resource that can be allocated by the own node. Allocate communication resources to the own node. Note that communication resources can be allocated not only because the own node possesses surplus communication resources in terms of capability, but also in addition to this, it is permitted to allocate communication resources from other nodes. Say.

  If the communication resource can be allocated to the own node (S103-YES), the communication resource is allocated to the packet transmission unit 17 of the own node (S104). On the other hand, when no more communication resources can be allocated to the own node (S103-NO), the communication resource allocation unit 15 reduces the amount of packets to be transmitted by the own node (decreases the transmission rate). A transmission amount reduction process for lowering the transmission rate is performed on an adjacent node that transmits a packet to the upper layer or the own node (S105). Details of this processing will be described later.

  In step S102, if the communication load is smaller than the communication resource, that is, if the number of packets in the packet buffer 13 is decreasing, the process proceeds to step S106, and the packet is transmitted to the upper layer of the own node or the own node. A transmission amount increasing process for notifying the adjacent node that the transmission rate may be increased is performed (S106). Details of this processing will also be described later.

  If the communication load and communication resources are balanced, that is, if the number of packets in the packet buffer 13 is not changed, this routine is terminated without performing any particular processing. The determination as to whether or not the number of packets accumulated in the packet buffer 13 has changed may be made with a certain margin.

[Transmission reduction processing]
Next, details of the transmission amount reduction process performed by the communication resource allocation unit 15 in step S105 will be described with reference to the flowchart of FIG.

  First, the communication resource allocation unit 15 examines the packets accumulated in the packet buffer 13 and calculates the number of packets from the node and the number of transmission source nodes related to the packet for each transfer source node (S201). ). The amount of packets accumulated in the buffer can be regarded as the transmission rate (proportional to) the transmission source node. Here, the transfer source node includes its own node. That is, the packet stored in the packet buffer 13 by the upper layer of the own node is also examined in step S201.

  After calculating the number of packets and the number of transmission source nodes for all transfer source nodes, the node having the largest number of packets per transmission source node is selected (S202). That is, the node with the highest transmission rate is selected as compared with the number of transmission source nodes. Here, when there are a plurality of nodes having the largest number of packets per source node, it is preferable to select the node having the largest number of packets stored in the packet buffer. In addition, when the number of stored packets is the same, one node may be selected at random.

  Then, it is determined whether the selected node is the local node (S203). If the selected node is the local node (S203-YES), the communication resource allocation unit 15 requests the higher layer to reduce the transmission amount (S205). ). On the other hand, if the selected node is not its own node (S203—NO), that is, if the selected node is an adjacent node, an instruction to reduce resources is transmitted to the selected node (S204). More specifically, the resource allocation instruction to the adjacent node is that the resource allocation packet generator 16 generates a packet (resource allocation packet) instructing resource reduction, and the packet transmitter 17 transmits this packet. Is done by.

  FIG. 5 is a diagram showing a message format of the resource allocation packet. As shown in FIG. 5, the resource allocation packet includes an IP header 51, a TCP / UDP header 52, a type 53 indicating whether to notify resource reduction or increase permission, time 54, and communication to which destination node A destination address 55 indicating whether to notify resource allocation and a resource change amount 56 indicating how much the allocated resource is to be reduced or increased are configured.

  In S204, a resource allocation packet for requesting resource reduction is generated, and the adjacent node that has received the packet decreases allocation of communication resources of the own node.

[Transmission increase processing]
Next, details of the transmission amount increasing process performed by the communication resource allocation unit 15 in step S106 will be described with reference to the flowchart of FIG.

  First, the communication resource allocation unit 15 examines the packets accumulated in the packet buffer 13, and calculates the number of packets from the node and the number of transmission source nodes related to the packet for each transfer source node (S301). ). Here, the fact that the own node is included in the transfer source node is the same as the transmission amount reduction process described above.

  After calculating the number of packets and the number of transmission source nodes for all transfer source nodes, the node having the smallest number of packets per transmission source node is selected (S302). That is, the node having the lowest transmission rate is selected as compared with the number of transmission source nodes. Then, it is determined whether or not the selected node is the own node (S303). If the selected node is the own node (S303-YES), the communication resource allocation unit 15 may increase the transmission amount to the upper layer. Notification is made (S305). On the other hand, if the selected node is not its own node (S303-NO), that is, if the selected node is an adjacent node, the selected node is notified that the resource may be increased (S304). ). In the same way as described above, the resource allocation packet generation unit 16 generates the resource allocation packet shown in FIG. 5 and the packet transmission unit 17 transmits the resource allocation packet to the adjacent node.

<Operation example>
An operation example of flow control in this embodiment will be described. Here, a case where four nodes of nodes 1, 4, 5, and 6 transmit packets to node D in the situation of the network topology shown in FIG.

  Here, the amount of communication resources is indicated by the amount of packets that can be transmitted per unit time, and the maximum number of communication resources that can be allocated between adjacent nodes is described as “4”.

  7a to 7g are diagrams for explaining changes in resource allocation, that is, changes in the transmission rate of each node. In FIG. 7a, all the nodes transmit packets at the maximum transmission rate, and the flow control is gradually effective, and in FIG. 7a to 7g show the number of packets (transmission rate) transmitted per unit time between nodes, the transmission source node of the packet, and the amount of communication resources allocated to each node. For example, in FIG. 7a, node 1 transmits four packets per unit time to node D, and the source nodes of these packets are nodes 1, 4, 5, and 6. It can also be seen that the communication resource amount assigned to the node 1 is “4”.

  In the situation of FIG. 7a, four or more packets per unit time are input to each of the nodes 1, 2, and 3, and packet dropping occurs here. Note that the number of packets received by the node 1 is four per unit time. However, since packets are also transmitted from the node 1 (applications thereof), packet drops occur.

  Therefore, the node 1 requests a resource reduction (transmission rate reduction) from the node 2 which is a transmission source node.

The node 2 also requests the source node to reduce resources. Here, the node 2 receives packets from the node 3 and the node 4, and determines to which node resource reduction is requested as follows. It can be seen that the packets received from the node 3 have two transmission source nodes, the nodes 5 and 6, and the number of packets (transmission rate) is “4”. On the other hand, it can be seen that the number of packets received from the node 4 is only one node 4 and the number of packets is “4”. Therefore, two packets are transmitted from the node 2 per source node, whereas four packets are transmitted from the node 4 per source node. Therefore, the node 2 transmits a request for resource reduction to the node 4 having a large number of transmission packets per transmission source node (a high transmission rate).

  The node 3 also requests the source node to reduce resources. At this time, the node 3 receives packets from the nodes 5 and 6, and receives four packets per source node from any node. Therefore, either node 5 or 6 may be requested to reduce the resource, and here, the node 5 is requested to reduce the resource.

  As shown in FIG. 7a, each node in which a packet drop occurs as described above transmits a resource reduction request to the adjacent node, resulting in the situation shown in FIG. 7b.

  In the situation shown in FIG. 7b, packet drop is eliminated in node 1 because the transmission rate from node 2 has fallen. On the other hand, since the packet drop has not been resolved in the nodes 2 and 3, further resource reduction requests are made to the adjacent nodes. The node 2 makes a resource reduction request to the node 4 that is transmitting three packets per transmission source node. Further, the node 3 makes a resource reduction request to the node 6 that is transmitting four packets per transmission source node.

  As a result, the situation shown in FIG. 7c is changed from the situation shown in FIG. 7b. Again, since packet drops have not yet been resolved at nodes 2 and 3, a resource reduction request is further made to the adjacent nodes. Node 2 receives two packets per source node from both nodes 3 and 4. Therefore, the node 2 makes a resource reduction request to the node 3 having a large amount of packets to be transmitted per unit time. Since the nodes 3 and 6 are transmitting packets under the same conditions, the node 3 may transmit a resource reduction request to either of the nodes 5 and 6. Here, a resource reduction request is transmitted to the node 5.

  As a result, the situation shown in FIG. 7d is changed from the situation shown in FIG. 7c. Again, since packet drops have not yet been resolved at nodes 2 and 3, a resource reduction request is further made to the adjacent nodes. Based on the same criteria as above, node 2 requests node 4 and node 3 requests node 6 to reduce resources.

  As a result, the situation shown in FIG. Again, since packet drops have not yet been resolved at nodes 2 and 3, a resource reduction request is further made to the adjacent nodes. Based on the same criteria as described above, the node 2 requests the node 3 and the node 3 requests the node 5 to reduce the resource.

  As a result, the situation shown in FIG. 7f is changed from the situation shown in FIG. 7e. At this point, the node 2 eliminates the packet drop. On the other hand, since the packet drop has not been resolved in the node 3, a resource reduction request is further made to the node 6.

  The situation finally becomes as shown in FIG. 7g, and the packet drop is eliminated also at the node 3, and the packet drop is eliminated at all the nodes. As shown in FIG. 7g, the transmission rate is controlled so that each of the nodes 1, 4, 5, and 6 transmitting packets to the node D transmits one packet per unit time. It can be seen that the flow control is executed so that the communication resources allocated to the original node are equalized.

<Action and effect>
According to the present embodiment, in a situation where communication is aggregated and packet drops occur, it is possible to eliminate the packet drop by controlling the communication resource allocated to each node and controlling the transmission rate. . As a result, it is possible to omit a retransmission process or the like accompanying a packet drop, so that efficient communication can be performed.

  In transmission rate control, flow control is performed so that the amount of communication resources allocated to each transmission source node is equalized. That is, as shown in FIG. 7g, all of the nodes 1, 4, 5 and 6 can communicate with the node D at the same transmission rate, and an equal communication opportunity can be obtained at each node.

  Furthermore, in this embodiment, each node simply instructs the adjacent node to change the transmission rate, and communication of the entire system is optimized. In addition, when requesting a change in transmission rate, each node determines which node to request a change in transmission rate based on only information that can be acquired within its own node, and communicates with other nodes. Is only a notification requesting resource reduction. Therefore, unnecessary communication does not occur for performing flow control, and overhead does not occur, so communication can be performed efficiently.

<Modification>
In the above description, when requesting reduction of communication resources, the communication resources are reduced by “1”. However, if the communication load is large, it may be requested to reduce a larger amount of communication resources. good. Whether or not the communication load is large can be determined by whether or not the increase amount of the amount of packets accumulated in the packet buffer is larger than a predetermined threshold.

  In the above description, the communication resource reduction is notified only to one of the adjacent nodes. However, a plurality of nodes may be requested to simultaneously reduce the communication resource. In particular, it is preferable to simultaneously reduce communication resources for a plurality of nodes when the communication load is large.

  According to these methods, it is possible to eliminate packet dropping more quickly.

  In the above description, the transmission rate of the adjacent node that transmits packets to its own node is determined based on the number of packets accumulated in the packet buffer 13, but more directly per unit time. You may judge by how many packets were received.

(Second Embodiment)
In the first embodiment, the flow control is performed so that the transmission rates of the transmission source nodes are equal. On the other hand, in this embodiment, flow control is performed so that the transmission rate per stream is equal. A stream is a pair of a transmission source node and a destination node, and even if packets are transmitted from the same transmission source node, they are different streams if the destinations are different.

  Since this embodiment is basically the same as the configuration of the first embodiment, different parts will be described. The difference between this embodiment and the first embodiment is the contents of the transmission amount reduction process (S105) and the transmission amount increase process (S106) in the flowchart of FIG.

The flowchart of the transmission amount reduction process for reducing the transmission amount of the own node in this embodiment is as shown in FIG. First, for each transfer source node, the communication resource allocation unit 15 calculates the number of streams transmitted by the transfer source node and the number of packets stored in the packet buffer 13 (S801). The number of streams is obtained by examining packets from a specific source node stored in the packet buffer 13 and examining how many types of destination nodes exist.

  Then, the communication resource allocation unit 15 selects a transmission source node having the largest number of packets per stream (S802). That is, when there are a plurality of transmission source nodes having the largest number of packets per stream, it is preferable to select the transmission source node having the largest number of packets in the packet buffer 13, and when this condition is also equal, transmission is performed randomly. You can select the original node.

  When the selected node is its own node (S803-YES), it requests the upper layer of its node to reduce the transmission amount (S805), and when the selected node is an adjacent node (S803-NO) ) Transmits a resource reduction instruction to the selected node (S804). The resource reduction instruction to the adjacent node is performed by transmitting the resource allocation packet generated by the resource allocation packet generator 16 as in the first embodiment.

  Further, a flowchart of the transmission amount increasing process in the present embodiment is as shown in FIG. Also in the transmission amount increase process, the number of streams and the number of packets are calculated for each transfer source node in the same manner as the above transmission amount reduction process (S901), and the node with the smallest number of packets per stream is selected. (S902). Then, it notifies the selected node that the transmission amount may be increased (S904 / S905).

  Next, an example of the flow control operation in the present embodiment will be described with reference to FIGS. 10a to 10f. Here, in the situation of the network topology shown in FIG. 10 a, four nodes 1, 2, 3, and 4 transmit a packet to node D, and node 3 also transmits a packet to node 1 An example will be described. In the situation shown in FIG. 10a, the nodes 1, 2 and 4 are communicating with only one stream, while the node 3 is communicating with two streams. In FIG. 10a, a packet represented by a square is addressed to node D, and a packet represented by a circle is addressed to node 1. The number shown in the packet is the source node number.

  In the situation illustrated in FIG. 10a, all nodes transmit packets at the maximum transmission rate (allocated resource amount “4”). Here, four packets are transmitted to the node 1 per unit time, and one packet is transmitted from the own node per unit time. However, since one of the received packets is addressed to the own node, the node 1 No packet dropping has occurred. On the other hand, in the node 2, since the amount of packets to be transferred exceeds the transmission rate, packet dropping occurs.

  Therefore, the node 2 requests the adjacent node of the own node to reduce the transmission rate in order to reduce the transmission amount. Since the node 3 performs communication of the two streams addressed to the node D and the node 1, and the transmission amount is “4” per unit time, the transmission amount per stream is “2”. On the other hand, the transmission amount of the node 4 is “4” for one stream communication addressed to the node D. Accordingly, since the transmission amount per stream is larger in the node 4, the node 2 requests the node 4 to reduce resources (decrease in transmission rate).

  As a result, as shown in FIG. 10B, the amount of communication resources allocated to the node 4 decreases to “3”, but packet dropping still occurs in the node 2. Here, since the transmission amount per stream is “2” and the transmission amount per stream is “3”, the node 2 requests the node 4 to further reduce resources. .

  As a result, the communication resource amount of the node 4 becomes “2” (FIG. 10c), but the packet drop at the node 2 has not been eliminated. Here, the transmission amount per stream is “2” for both the nodes 3 and 4, but the amount of packets from the node 3 is larger, so here the node 2 reduces the communication resources with respect to the node 3. Request.

  As a result, the communication resource amount of the node 3 becomes “3” (FIG. 10d), but the packet drop at the node 2 has not been eliminated. Here, since the transmission amount per stream is “1.5” in the node 3, the transmission amount per stream is “2” in the node 4, so the node 2 communicates with the node 4. Request resource reduction.

  As a result, the communication resource amount of the node 4 becomes “1” (FIG. 10e), but the packet drop at the node 2 has not been eliminated. Here, since the transmission amount per stream is “1.5” in the node 3, the transmission amount per stream is “1” in the node 4, so the node 2 communicates with the node 3. Request resource reduction.

  As a result, the communication resource amount of the node 3 becomes “2” (FIG. 10f). In this state, the packet drop at the node 2 is eliminated. As shown in FIG. 10e, the amount of communication resources allocated to any node is proportional to the number of streams with which that node is communicating. That is, flow control is realized so that the amount of communication resources (transmission rate) allocated per stream is equalized and equal communication opportunities are given to each stream (a pair of transmission / reception nodes).

(Third embodiment)
This embodiment is characterized in that each node sets a different communication resource amount (transmission rate) for each transfer destination node.

  Here, the situation shown in FIG. 11 will be described as an example. In FIG. 11, the node 1 performs communication with the node D1 and the node D2 as destinations, and the node 2 performs communication with only the node D1 as a destination. As shown in FIG. 11, the communication path from the node 1 to the node D1 and the node D2 branches at the node 3. On the other hand, the path from the node 1 to the node D1 and the path from the node 2 to the node D2 merge at the node 4.

  When the flow control is performed by the method described in the first and second embodiments, a packet drop occurs in the node 4, so the node 4 requests the node 3 (and the node 2) to reduce communication resources. . In accordance with this request, the node 3 reduces the communication resource and lowers the transmission rate. However, no packet drop occurs between the node 3 and the node D2, and it is not necessary to lower the communication transmission rate during this period.

  Therefore, each node has a setting of the communication resource amount to be assigned for each transfer destination node. Then, the node in which the packet drop has occurred requests an adjacent node to reduce the amount of communication resources allocated to communication with the local node as the transfer destination. In FIG. 11, the node 4 requests the node 3 to reduce the amount of communication resources allocated to communication with the node 4 as a transfer destination. The format of the communication resource allocation packet used in this embodiment is shown in FIG. The communication resource allocation packet in this embodiment is different from the above-described embodiment in that a transfer destination address 57 is provided instead of the destination address 55. In this field, it is stored which node is related to the allocation of the communication resource to which the packet is transferred.

In this way, by assigning different communication resource amounts for each transfer destination, the transmission rate to the transfer destination node with a large communication load is suppressed, and a large transmission rate is used for the transfer destination node with a low communication load. Communication can be realized. In the example of FIG. 11, the node 3 performs communication with the node 4 as the transfer destination at a lower transmission rate, but the communication with the node D2 as the transfer destination can be performed without particularly decreasing the transmission rate.

(Fourth embodiment)
The present embodiment is characterized in that each node sets a different communication resource amount (transmission rate) for each destination node.

  The situation shown in FIG. 11 will be described again by way of example. The node 3 can request the node 1 to reduce resources allocated to communication destined for the node D1. That is, the node 1 can maintain the transmission rate of the packet addressed to the node D2 by reducing only the transmission rate of the packet addressed to the node D1.

  In addition, in order to control the allocation of communication resources different for each destination node in this way, it is necessary to perform the flow control shown in FIG. 3 for each destination. That is, it is necessary to perform load determination and resource allocation control only for packets of a specific destination.

  In this way, by assigning different communication resource amounts for each destination, the transmission rate to a destination node with a large communication load is suppressed, and a large transmission rate is used for a destination node with a small communication load. Can be realized. In the example of FIG. 11, the node 1 performs communication destined for the node D1 with a reduced transmission rate, but communication destined for the node D2 can be performed without particularly reducing the transmission rate.

(Fifth embodiment)
In the above embodiment, the process of permitting the adjacent node to increase the transmission amount when the communication load on the own node is low (S106 in FIG. 3) is transmitted as shown in the flowcharts in FIGS. This is done by selecting the original node or the node having the lowest transmission rate per stream and permitting communication resource allocation to this node.

  However, there may be a case where the application of the node does not transmit at a very high transmission rate other than when the transmission rate is low because the communication resource of the selected node is insufficient. It is difficult for a node that permits an increase in the transmission amount to judge this difference, and it may happen that a node that does not require a high transmission rate is permitted to increase the transmission amount.

  Therefore, in the present embodiment, processing for permitting an increase in the transmission amount is performed as follows. That is, a node having a low communication load on the own node permits an increase in transmission amount, that is, an increase in allocated communication resources, to all adjacent nodes. As a result, the amount of transmission increases from a node whose transmission rate is suppressed due to a resource shortage, and the amount of transmission from a node originally having a low transmission rate from an application does not change. By permitting an increase in communication resources to be allocated to all adjacent nodes in this way, a node that requires an increase in communication resources can increase the allocation.

  In this way, by gradually allowing all adjacent nodes to increase the transmission amount, the amount of packets received by the own node increases, and eventually the communication load on the own node becomes overloaded. A resource shortage (packet dropping) occurs. As described above, when a resource shortage occurs in the own node, a more suitable resource allocation can be achieved by reducing the transmission rate for the transmission source node or the adjacent node having the highest transmission rate per stream. It becomes possible.

It is a figure which shows the example of the network topology of the radio | wireless communications system which concerns on 1st Embodiment. It is a figure which shows the functional block of the radio | wireless communication apparatus which concerns on 1st Embodiment. It is a flowchart which shows the flow of the process of flow (flow rate) control in 1st Embodiment. It is a flowchart which shows the flow of the process which reduces the transmission rate of the upper layer of an own node, or an adjacent node in order to reduce the transmission amount of an own node in 1st Embodiment. It is a figure which shows the format of the resource allocation packet in 1st Embodiment. It is a flowchart which shows the flow of the process which permits the increase in the transmission rate of the upper layer of an own node, or an adjacent node in order to increase the transmission amount of an own node in 1st Embodiment. It is a figure explaining the operation example of the flow control in 1st Embodiment. It is a figure explaining the operation example of the flow control in 1st Embodiment. It is a figure explaining the operation example of the flow control in 1st Embodiment. It is a figure explaining the operation example of the flow control in 1st Embodiment. It is a figure explaining the operation example of the flow control in 1st Embodiment. It is a figure explaining the operation example of the flow control in 1st Embodiment. It is a figure explaining the operation example of the flow control in 1st Embodiment. It is a flowchart which shows the flow of the process which reduces the transmission rate of the upper layer of an own node, or an adjacent node in order to reduce the transmission amount of an own node in 2nd Embodiment. It is a flowchart which shows the flow of the process which permits the increase in the transmission rate of the upper layer of an own node, or an adjacent node in order to increase the transmission amount of an own node in 2nd Embodiment. It is a figure explaining the operation example of the flow control in 2nd Embodiment. It is a figure explaining the operation example of the flow control in 2nd Embodiment. It is a figure explaining the operation example of the flow control in 2nd Embodiment. It is a figure explaining the operation example of the flow control in 2nd Embodiment. It is a figure explaining the operation example of the flow control in 2nd Embodiment. It is a figure explaining the operation example of the flow control in 2nd Embodiment. It is an example of the network topology for demonstrating the flow control in 3rd Embodiment. It is a figure which shows the format of the resource allocation packet in 3rd Embodiment. It is a figure which shows the condition where several nodes are communicating simultaneously with a specific node in an ad hoc network.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Packet reception part 12 Packet determination part 13 Packet buffer 14 Load determination part 15 Communication resource allocation part 16 Resource allocation packet generation part 17 Packet transmission part 18 Path | route storage part

Claims (9)

A wireless communication device in a wireless communication system configured by a plurality of wireless communication devices and performing communication between wireless communication devices by relaying one or more wireless communication devices,
Transmission rate management means for managing the transmission rate of the own node;
Receiving means for receiving packets from neighboring nodes;
Load determination means for determining the communication load of the own node;
When it is determined that the communication load of the own node is overloaded, a transmission rate suppression requesting unit that requests suppression of the transmission rate to an adjacent node that is transmitting packets to the own node;
Have
The transmission rate suppression requesting unit is configured such that, among a plurality of adjacent nodes transmitting a packet to the own node, the transmission rate of a packet transmitted from the adjacent node is compared with the number of transmission source nodes related to the transmitted packet. A wireless communication device that requests a specific adjacent node that is the highest adjacent node to suppress a transmission rate. A wireless communication device in a wireless communication system configured by a plurality of wireless communication devices and performing communication between wireless communication devices by relaying one or more wireless communication devices,
Transmission rate management means for managing the transmission rate of the own node;
Receiving means for receiving packets from neighboring nodes;
Load determination means for determining the communication load of the own node;
When it is determined that the communication load of the own node is overloaded, a transmission rate suppression requesting unit that requests suppression of the transmission rate to an adjacent node that is transmitting packets to the own node;
Have
The transmission rate suppression request means has the highest transmission rate of a packet transmitted from the adjacent node among a plurality of adjacent nodes transmitting packets to the own node as compared to the number of streams related to the transmitted packet. A wireless communication apparatus that requests a specific adjacent node that is an adjacent node to suppress a transmission rate. The transmission rate management means manages a transmission rate by adjusting resources allocated to communication,
The wireless communication apparatus according to claim 1, wherein the resource is at least one of a channel number, a bandwidth, a slot number, and a back-off time to be used. The transmission rate management means sets a transmission rate for each transfer destination to which a packet is transferred,
The wireless communication apparatus according to claim 1, wherein the transmission rate suppression requesting unit requests the specific adjacent node to suppress transmission of a packet having the local node as a transfer destination. . The transmission rate management means sets a transmission rate for each destination to which a packet is transmitted,
The load determination means determines a communication load for each destination node,
The transmission rate suppression request means determines the specific adjacent node for communication to the destination node determined to be overloaded, and requests the specific adjacent node to suppress the transmission rate to the destination node. The wireless communication apparatus according to any one of claims 1 to 3. A wireless communication method performed by a wireless communication device in a wireless communication system configured by a plurality of wireless communication devices and performing communication between wireless communication devices by relaying one or more wireless communication devices,
The wireless communication device is
Manage the transmission rate of its own node,
Receive packets from neighboring nodes
Determine the communication load of the own node,
When it is determined that the communication load of the own node is overloaded, among the plurality of adjacent nodes that are transmitting packets to the own node, the transmission rate of packets transmitted from that adjacent node A wireless communication method comprising: requesting a specific adjacent node that is the highest adjacent node relative to the number of transmission source nodes to suppress a transmission rate. A wireless communication method performed by a wireless communication device in a wireless communication system configured by a plurality of wireless communication devices and performing communication between wireless communication devices by relaying one or more wireless communication devices,
The wireless communication device is
Manage the transmission rate of its own node,
Receive packets from neighboring nodes
Determine the communication load of the own node,
When it is determined that the communication load of the own node is overloaded, among the plurality of adjacent nodes that are transmitting packets to the own node, the transmission rate of packets transmitted from that adjacent node A wireless communication method comprising: requesting a specific adjacent node, which is the highest adjacent node compared to the number of streams, to suppress a transmission rate. A wireless communication program in a wireless communication system configured by a plurality of wireless communication devices and performing communication between wireless communication devices by relaying one or more wireless communication devices,
For the wireless communication device,
Manage the transmission rate of its own node,
Receive packets from neighboring nodes,
Determine the communication load of the own node,
When it is determined that the communication load of the own node is overloaded, among the plurality of adjacent nodes that are transmitting packets to the own node, the transmission rate of packets transmitted from that adjacent node A wireless communication program characterized by causing a specific adjacent node which is the highest adjacent node as compared with the number of transmission source nodes to request suppression of a transmission rate. A wireless communication program in a wireless communication system configured by a plurality of wireless communication devices and performing communication between wireless communication devices by relaying one or more wireless communication devices,
For the wireless communication device,
Manage the transmission rate of its own node,
Receive packets from neighboring nodes,
Determine the communication load of the own node,
When it is determined that the communication load of the own node is overloaded, among the plurality of adjacent nodes that are transmitting packets to the own node, the transmission rate of packets transmitted from that adjacent node A wireless communication program characterized by causing a specific adjacent node that is the highest adjacent node compared to the number of streams to request suppression of a transmission rate.

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